The purpose of this study is to evaluate in detail the usability of new cellulosic fibers extracted from the stem of the plant Strelitzia reginae, as a potential reinforcement for polymer composites. The morphological, physical, thermal, and mechanical properties of fibers were addressed for the first time in this paper. Both untreated and alkali-treated fibers were characterized, using scanning electron microscopy (SEM), Fourier-transform infrared, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), optical microscope, and X-ray diffraction (XRD) and applying tensile test for determining the mechanical behavior. For both fiber treated at one hour (T1H) and at four hours (T4H), the stem anatomy and fiber SEM micrographs showed a strong presence of fiber cells. Thermogravimetry and DSC showed that the fiber was thermally stable up to 233°C for untreated fiber, 254 and 240°C, respectively, In single-fiber tensile tests, it was observed that the fibers extracted from the stem of Strelitzia reginae were strong. The mean values of Young’s modulus exhibited by untreated fibers and treated (T1H) and (T4H) are, respectively, 9.89 GPa, 12.08, and 18.39 GPa. Also mean values of tensile strength are 271.79, 306.23, and 421.39 MPa. The XRD reveals the presence of cellulose with a Crystallinity Index of 70% for raw fiber and 72% for the treated one. Fourier-transform infrared analysis well demonstrated the effect of chemical treatment. It can be concluded from the results of all above experiments that the Strelitzia reginae fibers (SR) could serve as a possible reinforcement in composite materials.

This work aims to study the effect of chemical treatments of date stone flour (DSF) as a filler on the elastic properties of biocomposites based on green epoxy resin (GER) used as a matrix. The main disadvantages of natural reinforcements in biocomposites are the poor compatibility between the reinforcement and the matrix as well as the relatively high moisture sorption. Different chemical treatments using soda (alkaline), benzoyl chloride, and potassium permanganate were applied to the DSF filler. Then, the filler was incorporated into the matrix at 30 wt % to obtain GER/DSF biocomposites. The elastic properties of the biocomposites, namely, longitudinal modulus, shear modulus, bulk modulus, Young's modulus of elasticity, acoustic impedance, Poisson's ratio, and ultrasonic microhardness, were determined using ultrasonic through-transmission method. In addition, the morphology was studied using microscopy analysis. The results obtained revealed a decrease of the elastic properties of the pretreated-filler biocomposite compared to the pure GER. On the other hand, the chemical treatment of the filler leads to an improvement of the elastic properties of GER/DSF biocomposites. The permanganate treatment is the most suitable for GER/DSF biocomposites. The morphology analysis through optical microscopy and scanning electron microscopy showed that chemical treatments enhance the interfacial adhesion between the DSF filler and the GER matrix.

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We have studied the magnetization hysteresis loops of a twinned and detwinned single crystals in a temperature range between 4.2 and 100 K and a magnetic field (H) range between 0 and 6 T. We carried out relaxation measurements on the samples at different temperatures and magnetic fields. We investigated the twin pinning as a function of temperature (T) and the fishtail anomaly in the critical current density of the two samples. We tried in this study to confirm or infirm the different models which explain the fishtail effect by confronting them to our experimental results We found that the collective creep theory is consistent with the results of our experiment in the field region where the magnetization is at its minimum. This field marks a crossover between the small and large bundle pinning regimes.